Modulating the Structural Properties of β-D-glucan Degradation Products by Alternative Reaction Pathways

The aim of the present study was to compare the degradation of β-D-glucan induced by hydroxyl radical to the degradation induced by heat treatment. β-D-Glucan was quickly and widely degraded by the action of hydroxyl radicals produced by a Fenton system at 85 °C, while thermal hydrolysis at 85 °C induced slow β-D-glucan depolymerization. The hydroxyl radical-induced degradation of β-D-glucan was accompanied by the formation of peroxyl radicals and new oxidized functional groups (i.e. lactones, carboxylic acids, ketones and aldehydes), as detected by ESR and NMR, respectively. In contrast, no changes in the monomer chemical structure of β-D-glucan were observed upon thermal hydrolysis. Therefore, different mechanisms are proposed for the oxidative cleavage of β-D-glucan, which are initiated by the presence of an unpaired electron on the anomeric carbon.